Insect GeneJuice Transfection Reagent (EMD, Madison, WI) is a liposome formulation optimized for maximum transfection efficiency and extremely low toxicity with Sf9, S21 and High Five (Invitrogen Corp., Carlsbad, CA) insect cells. The reagent is used for transient and stable transfections in serum-containing or serum-free media, and for co-transfection of transfer plasmids with linearized virus DNA for the production of recombinant baculoviruses. Insect GeneJuice is useful for large-scale protein expression in suspension-culture transfections of Sf9 insect cells using pIEx and pBiEx vectors or the dual-purpose pIEx/Bac vectors (EMD), all of which contain the immediate early baculovirus promoter, IE1.